Insulated panels are commonly used in sectional garage doors, curtain walls and the like.
Commonly, such panels utilize parallel, opposed, spaced-apart steel skins separated by a core of plastic foam. The foam is formed in situ and is bonded with the skins. The top and bottom marginal portions of the skins are bent inwardly to form perpendicular flanges. These flanges usually have an L configuration, so that the inner leg of the L extends parallel to the main plane of the skins. This parallel leg is buried in the foam core. The buried legs of the two flanges associated at one end of the panel are positioned in spaced apart relationship, to create a thermal break. Thus heat or cold affecting the exposed metal outer skin does not have a conductive connection with the inner skin.
A problem associated with such prior art panels is that the integrity of the panel depends on the adhesion between the metal skin and the plastic core. The panels can fall apart when the skin and core begin to separate in use.
U.S. Pat. No. 4,589,240, issued to Kendall et al., discloses a panel in which the associated flanges at top and bottom are formed to provide hook-shaped terminal portions. These hook means are engaged to mechanically interlock the skins. A thermal break is provided at each joint formed by the hook means. More particularly, an elongate vinyl element having a double C configuration is provided to fit like a sock over one of the hook means. The vinyl element includes a bead at an outer end spaced from the hook means, for serving as a weather seal. The core is pre-formed, rather than being foamed in-situ. This is done in part so that the skins can be pressed together to bring the hooks into engagement while compressing the core. The core then expands, when pressure is released, to "set" the hooks.